1. Field of the Invention
The present invention relates to a dynamoelectric machine such as an automotive alternator, etc., and particularly to an output terminal construction used to direct output power from the dynamoelectric machine to external equipment.
2. Description of the Related Art
In conventional automotive alternators, an external screw thread portion is disposed at an opposite end of an output terminal bolt from an output extraction end, the external screw thread portion of the output terminal bolt being fastened to a one-sided tightening nut secured by crimping to a penetrating aperture disposed on a positive-side cooling fin of a rectifier apparatus. At the output extraction end of the output terminal bolt, a wiring harness terminal is fastened with a nut by means of a first electrically-insulating bush made of a resin, a rear-end end frame, and a second electrically-insulating bush made of a resin. (See Patent Literature 1, for example.)
Patent Literature 1: Japanese Patent Laid-Open No. HEI 09-107654 (Gazette)
In conventional automotive alternators, a terminal that is electrically connected to the automotive vehicle wiring harness is inserted into the output terminal bolt and fastened with the nut to output electric power to automotive vehicle equipment. Now, in an electrical conduction pathway leading from the positive-side cooling fin to the output terminal bolt, a coupling portion between the external screw thread portion at the opposite end of the output terminal bolt from the output extraction end and the one-sided tightening nut interposes, and in an electrical conduction pathway leading from the output terminal bolt to the wiring harness terminal, a coupling portion between the external screw thread portion at the output extraction end of the output terminal bolt and the nut interposes. Electrical resistance at these coupling portions is large, increasing heat generated at the coupling portions during extraction of high-output electric current.
Thus, heat generated at the coupling portion at the opposite end of the output terminal bolt from the output extraction end gives rise to temperature increases in diodes constituting the rectifier apparatus that are disposed in close proximity to the output terminal bolt. Heat generated at the coupling portions at the output extraction end of the output terminal bolt also gives rise to heat degradation and thermal contraction of the electrically-insulating bushes made of a resin, loosening the coupling by the nut, thereby giving rise to reductions in force fastening the wiring harness terminal to the output terminal bolt.
Because the two electrically-insulating bushes are disposed so as to leave gaps in an axial direction of the output terminal bolts, the output terminal bolts, which have a higher electric potential than the rear-end end frame, are exposed at this portion. Thus, corrosion may arise in exposed portions of the output terminal bolts if the automotive alternator is used in an environment such as salt water, etc., giving rise to deterioration in electrical insulation.